B-1/B-2 visas are the most common nonimmigrant visas used for temporary entry into the United States. B-1 visas are typically used for business-related visits while B-2 visas are used for pleasure-related visits. With few exceptions, those who enter the U.S. must be in possession of a visa granted by a U.S. consulate abroad.

A visa merely permits one to apply for entry at a U.S. port of entry; it does not guarantee entrance. Immigration officials at the ports of entry determine whether a foreign national can enter the U.S. on the visa, and will set a definite period of time in which that person is authorized to remain in the U.S. (usually six months for those visiting for pleasure and 30-60 days for business visitors). The date by which one must depart from the U.S. is stamped on a document known as an "I-94 card". The time restriction applies even to foreign nationals who possess multiple-entry visas.